Cheating possible in this code?

Hello there!
I just started with Networking , and I am using RPC calls at the moment (I use Photon ).
Here is a little code, that , makes me curious if it can be cheated by players.

What it does, is ,the player sends an rpc to the server, then the server responds to the players for a limited time ( the rpc can be called only 4 times ). Can this be cheated?

using UnityEngine;
using System.Collections;

public class TestThing : Photon.MonoBehaviour {

	//by player
	float localvar = 12;
	//by server
	int server_times = 4;
	float server_var;

	// Update is called once per frame
	void Update () 
	{
		//we call the server only!
		if( Input.GetKeyDown(KeyCode.L) )
		{
			//request from server
			photonView.RPC( "ToServer",PhotonTargets.MasterClient );
		}
	
	}

	//this is what player requested
	//called on server only
	[RPC]
	void ToServer()
	{
		if( server_times >0 )
		{
			photonView.RPC( "ToPlayer" , PhotonTargets.Others , (object)20f );
			server_times -= 1;
		}
	}
	
	//called back on player ,after the player has requested it
	[RPC]
	void ToPlayer( float thevar )
	{
		localvar += thevar;
		print(server_times);
	}

}

It depends on what you mean with “can this be cheated?”. A client can send 10000 requests for this to the server if he wants, even if he only pressed the button once (or not times).